AGE-RELATED CHANGES IN FUNCTIONAL TEETH OF THE PACIFIC WALRUS (ODOBENUS ROSMARUS DIVERGENS)

摘要

Functional teeth (except for upper canines) of Pacific walruses that died or were harvested on the coast of Chukchi Peninsula in 2005, 2007-2008 and 2010-2011 were examined The dynamics of the annual cement increment was investigated. The rate of cement deposition on the walls of tooth roots significantly decreased with age. The rate of its deposition on the lingual side of upper teeth was much higher than on their buccal side, but it was similar on the lower teeth. The same cement layer deposited irregularly in different parts of a tooth (in its different sides and levels), with a general tendency of increasing the layer width from the top to the lower parts of teeth. As a result of local widening of some cement layers with age, the tooth surface became rough, knolls and rollers appeared there. As the age increased, external changes in teeth occurred they became larger, more roundish and heavier. A methodology of the preliminary determination of a relative walrus age based on the ratio between the cement and dentine widths on the attrition surface of lower teeth (without their cutting) is described.